The present invention relates to a demodulator for PSK-demodulating intermediate frequency (IF) signals of a PSK-modulated carrier with digital data, and more particularly to a demodulator of this kind using differential detection.
One of the prior art differential phase demodulators or differential detection demodulators of this kind achieves data demodulation by determining the phase variation during a one-baud interval after converting an IF signal into I and Q baseband channels. As will be explained in more detail below, such a demodulator involves the drawbacks of having complex configuration, which makes it difficult for the circuit to be arranged in small dimensions, and many aspects needing adjustment, such as the linearity and gain of the frequency discriminator and the balance between the I and Q baseband channels.
Another prior art demodulator which comprises a frequency discriminator and an integrate and dump (ID) circuit is subject to a greater error rate depending on the phase varying condition of input signals besides the need to adjust the constituent elements of the circuit to achieve overall characteristics of the demodulator.